Aroma chemicals with floral olfactory characteristics are of great interest to the perfume industry. Since the distillates or extracts of plants containing the appropriate characteristic fragrance are either very expensive--as is the case with attar of roses or jasmine-absolue-, or un-obtainable because of their instability- for example lilac or lily of the valley-, it has always been the aim of the aroma chemical industry to prepare synthetic substitute products. Whereas chemical partial or total synthesis already exist for most of the different active perfuming ingredients in stable plant distillates or extracts, and these are often suitable for manufacture, only technically stable, synthetic substitutes are available for the unstable natural fragrances such as lily of the valley or lilac, which may have a similar fragrance to the natural product but have a different structure. Examples of this kind of widely used sythetic aroma chemicals with floral olfactory characteristics include dimethyl-benzyl-carbinol (2) or phenylethyldimethyl-carbinol (3). The odour of compound 2 is described as warm, herbal-floral, slightly animal with a side note of freshly cut wood and nuances of lily and elder flower (S. Arctander, Perfume and Flavor Chemicals, 1969, Nr 989) Compound 3 (Arctander, Nr. 1043) has a floral, green slightly herbal and oily odour reminiscant of lily and hyacinth. Both compounds 2, 3 are only obtainable by means of Grignard-reactions, which require relatively sophisticated technology.
The secondary alcohols anologous to the tertiary alcohols 2 and 3 are not used in perfumes, however the corresponding primary alcohols 4 and 5 are. However the odour notes of these compounds are very different from those of 2, 3. ##STR3##
The odour of phenylethyl-alcohol (4), which is used in large amounts, is described as "mild and warm, rose- and honey-like" (Arctander, Nr. 2513). Dihydrocinnamic-alcohol (5) has an odour resembling cinnamon, described as "warm and mild, balsamic- floral, sweet" (Arctander, Nr. 2589). .alpha.-methyl-dihydro-cinnamic alcohol (6) prepared by means of aldol condensation of benzaldehyde and propionaldehyde with subsequent hydrogenation has a very week, cinnamon like-sweet, slightly woody odour and is not used as an aroma chemical.